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61 lines
1.9 KiB
C++
61 lines
1.9 KiB
C++
/*=============================================================================
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Copyright (c) 2015 Paul Fultz II
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lift.h
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Distributed under the Boost Software License, Version 1.0. (See accompanying
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file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)
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==============================================================================*/
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#ifndef FIT_GUARD_FUNCTION_LIFT_H
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#define FIT_GUARD_FUNCTION_LIFT_H
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/// lift
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/// ====
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///
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/// Description
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/// -----------
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///
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/// The `lift` operator will wrap a template function in a function object so it
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/// can be passed to higher-order functions. The `FIT_LIFT` macro will wrap the
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/// function using a generic lambda. As such, it will not preserve `constexpr`.
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/// The `FIT_LIFT_CLASS` can be used to declare a class that will wrap function.
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/// This will preserve `constexpr` and it can be used on older compilers that
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/// don't support generic lambdas yet.
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///
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/// Synopsis
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/// --------
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///
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/// // Wrap the function in a generic lambda
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/// #define FIT_LIFT(...)
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///
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/// // Declare a class named `name` that will forward to the function
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/// #define FIT_LIFT_CLASS(name, ...)
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///
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/// Example
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/// -------
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///
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/// auto my_max = FIT_LIFT(std::max);
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/// assert(my_max(3, 4) == std::max(3, 4));
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/// // Declare the class `max_f`
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/// FIT_LIFT_CLASS(max_f, std::max);
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/// assert(max_f()(3, 4) == std::max(3, 4));
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///
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#include <fit/returns.hpp>
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#include <fit/detail/forward.hpp>
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#ifdef _MSC_VER
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#define FIT_LIFT(...) [] { FIT_LIFT_CLASS(fit_local_lift_t, __VA_ARGS__); return fit_local_lift_t(); }()
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#else
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#define FIT_LIFT(...) [](auto&&... xs) FIT_RETURNS(__VA_ARGS__(FIT_FORWARD(decltype(xs))(xs)...))
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#endif
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#define FIT_LIFT_CLASS(name, ...) \
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struct name \
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{ \
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template<class... Ts> \
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constexpr auto operator()(Ts&&... xs) const \
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FIT_RETURNS(__VA_ARGS__(FIT_FORWARD(Ts)(xs)...)) \
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}
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#endif
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